I'm interested to hear this. I had very mixed experience a few years ago with the Seinxon finder card; it wasn't reliably in contact to make it beep, even when I was standing right beside it, but worse it would semi-regularly go into anti-stalker mode and start beeping and spamming iPhones around me with scary-looking notices. This second behaviour was obviously a deal-breaker so I discontinued use of them. (Looks like the company still exists but is now selling newer versions of the cards I bought from them)

Having recently switched to Android I was tempted to give Chipolo products a try, but this reddit thread disuaded me, as multiple users there are reporting the exact kinds of issues that I experienced previously: https://www.reddit.com/r/Chipolo/comments/1n4m4j3/chipolo_po...